forked from luck/tmp_suning_uos_patched
cc483f102c
The ext4 multiblock allocator decides whether to use group or file preallocation based on the file size. When the file size reaches s_mb_stream_request (default is 16 blocks), it changes to use a file-specific preallocation. This is cool, but it has a tiny problem. See a simple script: mkfs.ext4 -b 1024 /dev/sda8 1000000 mount -t ext4 -o nodelalloc /dev/sda8 /mnt/ext4 for((i=0;i<5;i++)) do cat /mnt/4096>>/mnt/ext4/a #4096 is a file with 4096 characters. cat /mnt/4096>>/mnt/ext4/b done debuge4fs -R 'stat a' /dev/sda8|grep BLOCKS -A 1 And you get BLOCKS: (0-14):8705-8719, (15):2356, (16-19):8465-8468 So there are 3 extents, a bit strange for the lonely 15th logical block. As we write to the 16 blocks, we choose file preallocation in ext4_mb_group_or_file, but in ext4_mb_normalize_request, we meet with the 16*1024 range, so no preallocation will be carried. file b then reserves the space after '2356', so when when write 16, we start from another part. This patch just change the check in ext4_mb_group_or_file, so that for the lonely 15 we will still use group preallocation. After the patch, we will get: debuge4fs -R 'stat a' /dev/sda8|grep BLOCKS -A 1 BLOCKS: (0-15):8705-8720, (16-19):8465-8468 Looks more sane. Thanks. Signed-off-by: Tao Ma <tao.ma@oracle.com> Signed-off-by: "Theodore Ts'o" <tytso@mit.edu> |
||
|---|---|---|
| .. | ||
| acl.c | ||
| acl.h | ||
| balloc.c | ||
| bitmap.c | ||
| block_validity.c | ||
| dir.c | ||
| ext4_extents.h | ||
| ext4_jbd2.c | ||
| ext4_jbd2.h | ||
| ext4.h | ||
| extents.c | ||
| file.c | ||
| fsync.c | ||
| hash.c | ||
| ialloc.c | ||
| inode.c | ||
| ioctl.c | ||
| Kconfig | ||
| Makefile | ||
| mballoc.c | ||
| mballoc.h | ||
| migrate.c | ||
| move_extent.c | ||
| namei.c | ||
| resize.c | ||
| super.c | ||
| symlink.c | ||
| xattr_security.c | ||
| xattr_trusted.c | ||
| xattr_user.c | ||
| xattr.c | ||
| xattr.h | ||